1. And its environmental impact
Mining
And its environmental impact

2. Outline 1. Types of Mining (and why we use them) 2. Beneficiation
3. Smelting
4. Environmental Concerns of 1 through 3

3. What determines the type of mining?
Underground v.s. Surface Mining v.s. Solution
Depth of below surface
Size of the ore body
Shape of the ore body
Grade
Type of Ore

4. Depth and Size

5. Shape of Ore Body

6. versus

7. Type of Ore Is the ore mineral soluble in water?
Can the ore be melted?

8. What are the types of mining?
Surface
Strip
Open Pit
Placers--Dredging
Underground
Solution

9. When do you use Surface Mining?
Large tonnage
High rates of production
Overburden (including rock) is thin

10. Strip Mining of Coal
Kansas Geological Survey

11. Open Pit Mining

12. Bingham Pit

13. Bingham from the air: Google Earth

14. Some photos and machinery used in open-pit mining

15. Photo I took at Bingham. 4 km in diameter 1 km in depth, at its zenith 400000 tons of rock per day

16. ?Dinky Toy?

17. Drilling in pit

18. Crushing in pit

19. Loading ore in pit

20. Underground Mining

21. When do we mine underground?
The ore deposit is deep
Ore body is steep
Grade is high enough to cover costs

23. Some types of underground mining
Room and Pillar
Cut and Fill
Long wall (coal)
Shrinkage Stoping
Block Caving

24. Room and Pillar
Tabular, shallow, strong

25. Cut and Fill

26. Long Wall

27. Shrinkage Stoping
Steeping dipping ore

28. Block Caving

29. Solution Mining

30. Beneficiation
Means of separation of ore mineral from waste material (or gangue minerals)
Also known as Liberation

31. What does it entail? Crushing and Grinding Separation
Ball mill or rod mill
Separation
Density (e.g. diamonds with a jig)
Magnetic properties
Electric properties
Surface properties

36. Refining the Ore Smelting Heap Leaching
removes the metal from the ore mineral by a variety of ways
Heap Leaching
removes metal from the ore by solution

37. Iron in review Blast Furnace 3CO + Fe2O3 2 Fe + 3CO2 (gas)

38. Sulphide Minerals Are sometimes roasted
Heated in air without melting to transform sulphides to oxides
Gives off H2S and SO2
Then oxides processed like Fe

39. Sulphides cont’d
Process of roasting and smelting together creates a matte
Sulfides are melted into a matte and air is blown through. S is converted to sulfur dioxide and Fe to iron oxide, and Cu and Ni stay in melt

40. Smelting

41. Result at Kidd Creek

42. Sulphides cont’d Solvent extraction/electroplating
Used where rock contains Cu but in too little amounts to be recovered by classical methods

44. Heap Leaching
In this process, typically done for Au, the ore is not ground, but rather, crushed and piled on the surface.
Weak solutions of NaCN (0.05%) percolate through the material leaching out the desired metals.
The solutions are collected and the metals are precipitated

45. Potential Environmental Problems
A. Mining operation itself
Disposal of a large amount of rock and waste
Noise
Dust
Beneficiation
Smelting and refining

46. From Underground Mining
Subsidence
Block/caving
Room and pillar
Salt mining (Droitwich)

47. Subsidence in rancher’s field

48. Subsidence from Pb-Zn mining

49. From Underground Acid Mine Drainage FeS minerals in coal
Sulphide deposits
Acidic streams can pick up heavy elements and transport them

50. Rock that has acid forming material

51. Drainage

52. Acid and open pits
Berkley Pit

54. Other problems with open pits
Very large holes
Pit slopes steep and not stable. Cannot be maintained
May fill with water
Strip coal mines –loss of top soil in past
Now smoothed out and top soil added

55. Disposal of Waste Rock More problematic for open pit than underground
Waste rock piles have steep angle of repose and thus may not be stable
Bingham in its hay day produced 400,000 tons of waste rock per DAY!

56. Tailings ponds From concentrating usually have high pH
At Bingham acid waters mixed with tailings water to neutralize
Different metals have different problems

57. Problems with Smelting/Roasting
Air: SO2 and CO2 and particulate matter
Noranda Quebec used to have the highest single point source of SO2 in the world. It may have been surpassed.
CN (Au); NaOH and F (Al); solvents (electrotwinning); heavy metals; oil and grease